Piezoelectric crystal holder



March 1946- s. A. BOKOVOY ET AL 2,395,841

PIEZOELECTRIC CRYSTAL HOLDER Filed Dec. 6, 1943 INVENTORS ATTHHNEY- Patented Mar. 5, 1946 PIEZOELECTRIC CRYSTAL HOLDER Samuel Alexander Bokovoy, Verona, and Kenton Kltch Garrison, East Orange, N. J.,'assignors to Federal Telephone and Radio Corporation, New York, N. Y., a corporation of Delaware Application December 6, 1943, Serial No. 513,140

Claims.

This invention relates in general to oscillator or resonator units for crystal controlled oscillator circuits and the like and consists of an improved formation of crystal element and coacting holder therefor designed to offer material advantages in its use. A special object of the present improvements is to provide a simple and economically made unit assembly having an improved supporting arrangement for the crystal element and of a character which in operation will restrain or damp the vibration of the crystal element to a minimum or negligible degree.

The improved .resonator unit consists of a substantially rectangular crystal element of special formation having its opposite ends of tapered or blunt chisel formation immediately at the end portions thereof adapted to be supported in an.

improved holder. The latter is preferably formed to provide a rectangular closed chamber for the crystal element, disposed in an oblique position therein, and is provided with an improved arrangement for making electrical contact with the opposite metalized or electrode surfaces of the crystal at one end thereof only and in a manner to effect an improved resilient pressure wiping contact with the electrode crystal surfaces. The improved arrangement accordingly provides a desirable type of contact fo efficient electrical connection with the crystal element having a desirable range of self adjustment to accommodate variations in production tolerances. Moreover the pressure contact is confined to the extremity of the crystal at one end portion only and in a manner which will reduce to the minimum damping.

effect on the crystal vibration which may be of the shear mode. The natural vibration is unimpeded and unrestrained to a materially improved degree by the elimination of any substantial pressures longitudinally of the crystal element as is characteristic of certain contact arrangements or by laterally applied resilient or compressive forces acting on the outer plane surfaces peculiar to other types of contact as heretofore used.

The present improvements further include special features contributing to simplicity of design and for maintaining all the parts in their properly assembled relation so as to be securely positioned without danger of dislodgement such as to interfere with proper operation and which may occur from external shocks under conditions of use. The improved assembly further is of a design which will readily accommodate crystal of different thickness and dimensions such as to permit a desirable range of adjustment of oscillation values to meet varied circuit conditions or requirements.

The foregoing and other features and advantages of the present invention will be more fully understood by reference to the accompanying drawing wherein like reference characters are applied to the corresponding parts in the several views.

In the drawing:

Fig. 1 is a view in side elevation having a portion of the holder member broken away and showing a desirable embodiment of the features of the invention.

Fig. 2 is a similar view having the lower portion thereof shown in vertical section centrally through the socket portion.

Fig. 3 is a horizontal sectional view taken on line 3-3 of Fig. 1.

In th preferred structural employment of the invention as illustrated the crystal resonator unit is illustrated as of the plug in type comprising a holder or container of insulating material consisting of a rectangular body portion l formed with an integral finger grip extension 2. a rectangular recess or opening 3 and having apertures 4-4 for the reception'of the terminal pins 55' for plug electrical connection. The rectangular recess 3, provided for the reception and support of the crystal element, is a shown open at the front face of the holding body member and is closed as a sealed chamber after assembling of the parts by means of a complemental face plate 6, secured by screws ll passed through the body and threaded to the plate and with a sealing washer 8 interposed between the body and plate as shown.

In accordance with the present improvements and for the purpose of providing for an effective supporting and electrical contact engagement with the crystal and the minimum restrictive influence upon the natural vibration of the crystal body throughout the length thereof, a specialform of crystal is provided together with an improved design and arrangement of contact elements. As shown the crystal oscillator or resonator element is of elongated rectangular plate form, formed of quartz crystal having its opposite or plane surfaces coated with the usual metallic electrodes ill, such as silver. The marginal edged portions of the crystal at the ends are s Shown inclined or tapered to be of blunt chisel-like formation. The electrode coatings may desirably be extended the full length of the crystal and over the beveled portions l2 but with suitable spacing at the ends thereof fo electrical separation. Th crystal or resonator element is as shown positioned obliquely within the recess with one end thereof held or confined by the rectangular corner walls of the socket and the opposite end thereof is positioned to be engaged by the electrical contact elements in the improved arrangement as shown.

The improved form and structural arrangement of the contact elements are designed for effective cooperation with the special crystal form to effect good electrical contact with the electrodes at one of the beveled end surfaces only and with an angularity of contact engagement adapted, in the securing and contact engagement, to reduce the compressive force on the crystal longitudinally thereof. The cooperating contact elements consist of a right angular rigid contact fitted to the lower right hand comer of the socket and composed of an internally threaded horizontal flange portion II and the integral laterally spaced vertical flanges or bars IS. The rigid contact is secured in position by the threaded engagement therewith of the terminal pin 5' as best shown in Fig. 2. Positioned to cooperate therewith there is provided the resilient or spring contact Hi, apertured at its left end portion to receive the threaded end of terminal pin 5 and rigidly secured in position by the nut I8 threaded to the pin. This spring contact element is formed with an engaging tip portion [9 disposed in acute angular relation to the engaging surface of the rigid contact flanges i5 and with the intermediate or connecting portion upturned to provide a bearing shoulder portion 20 positioned in engagement with the central boss or shoulder 2| formed on the chamber body and adapted by this engagement to secure the spring contact from lateral displacement. As will be seen by reference to Fig. 3 the width of the engaging tip portion is of the spring contact is such as to permit of its being received between the flanges I! of the rigid contact in electrically spaced relation from which it results that the upper electrode of the resonant element engages the flanges ll of the one contact while the lower electrode is engaged by the spring contact element in a manner to complete the circuit through the resonant element or crystal. The improved contact and securing engagement with the crystal as thus afforded, in addition to reducing axial pressure on the crystal, further provides for electrical contact engagement with the electrode at the beveled end portions inwardly of the outer or maximum plane of vibration of the crystal or inwardly toward its neutral axis thereby obtaining electrical contact with a minimum restrictive influence upon the natural vibration.

It is accordingly particularly advantageous for mounting of crystals having vibrations in the shear mode. The improved design and arrangement as shown readily accommodates itself to reasonable variations in the size of the crystals without impairing the advantages and in its assembly is of a character to securely position the parts in their operating relation without danger of displacement in use.

Having described our invention we claim:

1. A frequency determining unit of the character described comprising a container providing a recess for the reception of a resonant element, 2. crystal element positioned in the recess operative engagement with the crystal and comprising electrode engaging portions extending in substantially right angular relation and podtioned to engage the bevel electrode extensions and at least one of said contacts being resilient.

2. A frequency determining unit of the character described comprising a container providing a recess for the reception of a resonant element, a crystal element positioned in the recess and provided with electrodes on its opposite faces and having opposite ends with beveled edge portions and with the electrodes extended thereon, electric contact elements positioned for cooperative supporting and circuit closing engagement with the crystal element and having electrode engaging portions positioned in substantially right angular relation to engage the respective electrodes on the opposite bevel extensions thereof at one end only of the crystal and means in said container for engaging the crystal element to hold it in position.

3. A frequency determining unit of the character described comprising a container formed to provide a recess for the reception of a resonant element, a crystal element adapted for vibration in the shear mode positioned in the recess and provided with electrodes on its opposite faces and formed at its ends with beveled edge portions with the electrodes extended thereon, electric contact elements positioned for cooperative engagement with the crystal element and comprising electrode engaging portions in substantially right angular relation to engage the bevel electrode extensions and said engaging portions being laterally spaced for electrical separation.

4. A frequency determining unit of the character described comprising a container body formed with a substantially rectangular recess for the reception of a resonant element, a. crystal element positioned in the recess diagonally thereof with the supporting engagement in one corner of the recess, said crystal element being provided with electrodes on its opposite faces and formed at its ends with beveled edge portions with the electrodes extended thereon, electric contact and supporting elements positioned in the diametriand provided with electrodes on its opposite faces cally opposite corner of the recess from the supporting corner aforesaid, said contact elements comprising a stationary angular member having laterally spaced vertical contact'bars and a resilient contact element having a contact portion positioned to project between the bars and to have an acute angular relation thereto and terminal members connected to the respective contact elements.

5. A piezoelectric frequency determining element comprising an elongated rectangular crysto! plate provided with electrode coatings on its opposite faces and formed at least at one end with a beveled edge portion with the electrode coating extended thereon.

6. A piezoelectric frequency determining element comprising an elongated rectangular plate crystal provided with electrode coatings on its opposite faces and formed at least at one end with beveled ed e portions with the electrode coatings extended thereon.

'7. A piezoelectric frequency determining element comprisingan elongated rectangular plate crystal provided with electrode coatings on its opposite faces and formed at its opposite ends with beveled edge portions and having the electric coatings coextensive with the-beveled portions substantially as described.

8. A frequency determining unit of the charpositioned to engage the electrodes at one edge surface of the crystal only.

9. A frequency determining unit of the character described comprising a container providing a chamber for the reception of a resonant element, a crystal element positioned within the chamber and provided with electrodes on its 0pposite faces and formed with a beveled edge over which the electrodes are extended, electric contact elements positioned for cooperative engagement with the crystal and comprising electrode engaging portions engaging the opposite electrode extensions to be in relativel sharp angular rela- I tion to the electrode surfaces engaged thereby, at least one of said contacts being resilient and said contacts being positioned to engage the electrodes at one edge surface of the crystal only.

10. A frequency determining unit of the character described comprising a container providing a rectangularchamber for the reception of a resonant element, a crystal element positioned obliquely within the chamber and provided with electrodes on its opposite faces, electric contact elements positioned for cooperative supporting engagement with the crystal and comprising electrode engaging portions in relatively small angular relation to opposite electrode surfaces en- Based thereby at least one of said contacts being resilient and said contacts being positioned to engage the electrodes at one edge surface of the crystal only.

SAMUEL ALEXANDER BOKOVOY. KENTON KITCH GARRISON. 

